Comparison of 3 Interpretation Criteria for ⁶⁸Ga-PSMA11 PET Based on Inter- and Intrareader Agreement

Abstract

PET using radiolabeled prostate-specific membrane antigen (PSMA) is now being more widely adopted as a valuable tool to evaluate patients with prostate cancer (PC). Recently, 3 different criteria for interpretation of PSMA PET were published: the European Association of Nuclear Medicine (EANM) criteria, the Prostate Cancer Molecular Imaging Standardized Evaluation criteria, and the PSMA Reporting and Data System. We compared these 3 criteria in terms of interreader, intrareader, and intercriteria agreement. Methods: Data from 104 patients prospectively enrolled in research protocols at our institution were retrospectively reviewed. The cohort consisted of 2 groups: 47 patients (mean age, 64.2 y old) who underwent Glu-NH-CO-NH-Lys-(Ahx)-[ 68 Ga(HBED-CC)] (68 Ga-PSMA11) PET/MRI for initial staging of biopsy-proven intermediate-or high-risk PC, and 57 patients (mean age, 70.5 y old) who underwent 68 Ga-PSMA11 PET/CT because of biochemically recurrent PC. Three nuclear medicine physicians independently evaluated all 68 Ga-PSMA11 PET/MRI and PET/CT studies according to the 3 interpretation criteria. Two of them reevaluated all studies 6 mo later in the same manner and masked to the initial reading. The Gwet agreement coefficient was calculated to evaluate interreader, intrareader, and intercriteria agreement based on the following sites: local lesion (primary tumor or prostate bed after radical prostatectomy), lymph node metastases, and other metastases. Results: In the PET/MRI group, interreader, intrareader, and intercriteria agreement ranged from substantial to almost perfect for any site according to all 3 criteria. In the PET/CT group, interreader agreement ranged from substantial to almost perfect except for judgment of distant metastases based on the PSMA Reporting and Data System (Gwet agreement coefficient, 0.57; moderate agreement), in which the most frequent cause of disagreement was lung nodules. Intrareader agreement ranged from substantial to almost perfect for any site according to all 3 criteria. Intercriteria agreement for each site was also substantial to almost perfect. Conclusion: Although the 3 published criteria have good interreader and intrareader reproducibility in evaluating 68 Ga-PSMA11 PET, there are some factors causing interreader disagreement. Further work is needed to address this issue.

Interobserver agreement of [68Ga]Ga-PSMA-11 PET/CT images interpretation in men with newly diagnosed prostate cancer

“…Agreement for the detection of extra-pelvic nodes and distant metastases (miM) was almost perfect; the agreement for the presence or not of metastases was concordant for all patients (37/43 M0 and 6/43 M1a/1b). This result is in line with a previous study, and accurate interpretation of the presence or not of distant metastases is of particular importance as it has significant impact on treatment decision, ruling out surgical option [12,19].…”

“…Additionally, we demonstrated inter-reader substantial agreement with a less experienced physician resident with 2-year experience [20]. Our results are in line with Toriihara et al who showed at least substantial agreement of PROMISE and PSMA-RADS criteria in a group of patients (n = 47) who underwent [ 68 Ga]Ga-PSMA-11 PET combined with magnetic resonance imaging for initial staging; a point-by-point comparison of the results of Toriihara et al and ours is presented in Additional file 1: Table S4 [12].…”

“…However, qualitative examination is usually based on the detection of focal [ 68 Ga]Ga-PSMA-11 uptake higher than prostatic surrounding background [5,19,[21][22][23]. Disagreement in the interpretation of prostatic lesions was also pointed out by Toriihara et al and might have been due to differences in interpretation of moderate foci or diffuse uptake [12]. Therefore, criteria should be further refined in order to describe clinically important PC as it has been demonstrated with multiparametric magnetic resonance imaging of the prostate [24].…”

“…The inter-reader agreement of the PC molecular imaging standardized evaluation (PROMISE) proposed by Eiber et al was substantial for interpretation of [ 68 Ga]Ga-PSMA-11 PET/CT in a population of patients with biochemically recurrent PC [7,10], though authors recently showed that PROMISE criteria agreement was significantly lower for [ 18 F]fluciclovine than for [ 68 Ga]Ga-PSMA-11 [11]. More recently, Toriihara et al tested the three standardised interpretation criteria proposed by Fanti et al, Rowe et al and Eiber et al in a population of patients who underwent either [ 68 Ga]Ga-PSMA-11 PET/MR for PC primary staging or [ 68 Ga]Ga-PSMA-11 PET/CT for recurrent PC [12]. They revealed at least substantial agreement of the three classification systems, except in the evaluation of distant metastases based on PSMA-RADS [12].…”

“…More recently, Toriihara et al tested the three standardised interpretation criteria proposed by Fanti et al, Rowe et al and Eiber et al in a population of patients who underwent either [ 68 Ga]Ga-PSMA-11 PET/MR for PC primary staging or [ 68 Ga]Ga-PSMA-11 PET/CT for recurrent PC [12]. They revealed at least substantial agreement of the three classification systems, except in the evaluation of distant metastases based on PSMA-RADS [12].…”